1. Field of the Related Art
The present invention relates to a measuring device and a measuring method for adjusting a scanning optical system which scans with a light beam, and particularly to a scanning optical system measuring device and a scanning optical system measuring method which can be applied to an image forming apparatus or the like having a scanning optical system such as a laser beams printer.
2. Description of the Related Art
At the time of assembling an image forming apparatus, an optical scanning system must be adjusted to properly scan a photoconductor with a light beam. Traditionally, a device as shown in FIG. 12 is known as a measuring device for this adjustment of the scanning optical system.
In the measuring device shown in FIG. 12, facing a scanning optical system unit 1, two-dimensional position detection devices 5 which are plural photodetector devices are arranged along the scanning direction at positions where photoconductors are arranged, and the scanning state is measured on the basis of the light receiving position of each two-dimensional position detection devices 5. As the scanning state, the image forming position, tilt of the sub scanning line and curving of the scanning line of the scanning optical system unit 1 are measured.
Detection signals detected by the two-dimensional position detection devices 5 are processed by a signal processing circuit 6 and then taken into a computer 8 via an interface board 7, and predetermined measuring processing is carried out. In this case, since the computer 8 detects the light receiving position for each of the two-dimensional position detection devices 5, a light beam static mechanism 4 is controlled by a motor controller 9 to stop the rotating operation of a rotary polygon mirror and to define the stop position at a predetermined position so that a light beam is made incident on a two-dimensional position detection device as a detection target.
As another technique, JP-A-8-262350 is known. This technique uses a CCD device as a photodetector device and carries out measurement with a rotary polygon mirror in the rotating state. Therefore, a scanning timing detecting unit which detects the scanning timing of a light beam is provided, and the light detection timing is controlled synchronously with the scanning timing of the light beam.
However, in the former measuring method using the two-dimensional position detection devices, since their light receiving positions are detected, a large amount of arithmetic operation is necessary and the detection processing time is long. Therefore, as described above, in the case where a light beam is made incident on the two-dimensional position detection devices, the light beam must be made static during the time required for the processing. The light beam static mechanism 4 and its control mechanism require high costs, and it takes a long time to perform induction processing of the light beams to the two-dimensional position detection devices and signal processing, thus causing the adjustment time to be long. For example, an adjustment operator cannot make adjustment while visually recognizing the result of the adjustment operation in real time. As a result, there is inconvenience that the adjustment operation is difficult.
On the other hand, in the latter technique, the CCD device is used and the measuring resolution is one pixel of the CCD. Therefore, a target measuring accuracy cannot be achieved in some cases, and large-scale computer software for image processing of measurement data is required, thus increasing the cost of the device. Moreover, since the synchronization timing must be taken, there is inconvenience that signal processing between the scanning timing detecting unit and the measuring CCD driving unit is very complicated.